Typical processing in substrate process chambers causes various deposits to form on the process chamber walls. These deposits are generally removed by a cleaning process run in the chamber without a substrate present. One such cleaning process, used for example in epitaxial deposition systems, involves hydrogen chloride (HCl) and high temperature.
The cleaning process must be performed for a sufficient time to ensure that the internal process chamber surfaces and components are clean. In some instances, the cleaning process may be performed for too long of a period, which not only removes the unwanted deposits, but also may cause a significant amount of degradation of chamber surfaces and components. On the other hand, if the cleaning process is performed for too short of a period, a significant amount of deposits may remain on the process chamber surfaces, resulting in an increase in process drift and/or defects (e.g., particles). Thus, a balance is generally established between tolerating process drift and increased defects and the need to increase the lifetime of chamber components.
One method for finding the balancing point is to perform visual observations after an extended period of time. However, this is generally a subjective process and is prone to errors. Another method for finding the balancing point is to rely on process/defect trends (as substrates are being processed). However, this is tedious and causes unnecessary usage of substrates and resources.
Thus, the inventors have provided improved methods and apparatus for determining the endpoint of chamber cleaning processes.